1. Field of Invention
The invention relates to integrated electrical and/or electronic circuits.
2. Description of Related Art
Systems for protecting functional systems against overvoltages are known. Here, one may cite U.S. Pat. No. 3,737,725 which describes a circuit overvoltage protector having a fuse and a zener diode arranged in the electrical supply circuit of the functional module.
Also, designers of integrated electrical and/or electronic circuits often provide electrical terminals to one or more functional modules of an electrical and/or electronic system, in addition to electrical power supplies. Such external electrical terminals prove necessary, for example, for programming or configuring the functional module, to input a specific code into the system (and/or to a user), or to test, measure, and/or calibrate the functional module.
When the testing, calibration, or programming phase is complete, it may be desirable effectively to isolate the functional module from elements outside of the functional module or the electrical system. In other words, it is necessary to eliminate the external electrical terminal to prevent changes in the programming, configuration, or coding and/or to ensure better protection for the functional module, particularly against powerful electromagnetic fields and/or ultraviolet radiation which may be encountered in an industrial setting for example. Such isolation is also required in very harsh environments such as those that may be encountered in the space and nuclear arenas.
Various techniques have already been proposed to achieve this result. Thus, numerous devices that program by isolation are known. They generally call on physical circuit-breaking techniques, for example, using mechanical methods for applying laser beams, electrical segmentation using semiconductor switches, or by inhibiting logical accesses from the nonvolatile memory programming. The first method has the advantage of physically breaking off access to the terminal. However, it has the disadvantage of being implemented only when the electrical and/or electronic system is being manufactured, and before the system housing and/or protective device is sealed with resins or varnishes. Hence, this technique cannot be used by the end user, who is thus, unable to carry out the programming, configuration, or testing operations listed above.
The second set of techniques, based on the programming of memories or semiconductor switches, also has several drawbacks. To begin with, these techniques call on sophisticated, fragile, relatively expensive, and sometimes bulky components. They also do not enable their own programming to be protected by radically eliminating access paths.
Moreover, the technology based on floating-grid cells that is generally used has the drawback of substantial sensitivity to harsh environments, powerful electromagnetic fields, and ultraviolet radiation.
The main aspect of the invention is to overcome these drawbacks of the prior art. More specifically, one of the aspects of the invention is to provide a technique that effectively eliminates the external electrical terminal connected to a functional module that needs to be isolated (for example, after a testing, measurement, calibration, programming, configuration, or coding, etc. phase).
An additional aspect of the invention is to provide such a technique permitting utilization in harsh environments and/or in the presence of electromagnetic field(s) and/or high environmental radiation.
Another aspect of the invention is to provide such a technique whose cost, development, and/or implementation are reduced by comparison to known techniques.
Another aspect of the invention is to provide a device for electrical isolation of a functional module enabling the functional module to be programmed (particularly the decision as to the moment in time of isolation) by the end user.
These various aspects, as well as others that will emerge in the following text, are achieved according to the invention with the aid of an integrated electrical and/or electronic system that has at least one functional module connected to a supply voltage and connected via a pin external to the functional module by an electrical terminal. An isolation device electrically isolates the electrical terminal from the functional module, The isolation device may include a fuse whose first pole is connected to the pin of the functional module and the second pole corresponds to the external electrical terminal, a first semiconductor dipole that can be energized by a priming voltage, a first pole of which is connected to the first pole of the fuse and the second pole is externally accessible to the system, and a second dipole whose first pole is connected to the pin of the functional module and the second pole is connected to a preset voltage.
Therefore, application of a sufficient isolating voltage relative to the priming voltage between the second pole of the fuse and the second pole of the energizable semiconductor dipole causes the fuse to break physically, and thereafter, a preset voltage on the pin is exclusively maintained via the second dipole. Thus, after the fuse has broken, this voltage enables the operation of the functional module to be controlled.
The general principle of the invention is thus based on the combination of three single components (a fuse, an energizable semiconductor dipole, and a second dipole). By internally or externally controlling the breakage of the fuse, such a combination enables the functional module to be electrically isolated permanently at the desired point in time.
It is thus possible to program the moment in time at which the fuse breaks either by external, for example, human, intervention by manually operating an adequate isolating voltage or by internal control, for example, with the development of one or more particular conditions linked to the environment causing an isolating voltage to be generated.
It is important to note that exceeding a threshold voltage (imposed by the presence of the energizable semiconductor dipole) is necessary for programming the prohibition of electrical terminal to the functional module. As long as the fuse has not been broken, neither the fuse nor the dipoles disrupts operation of the system, and access to the functional module is direct.
Since the isolating voltage can be applied to the electrical terminal from the outside the system or the functional module, this system has the advantage of being accessible by the end user before this electrical terminal is eliminated, and prohibits all electrical terminals to the functional module. Electrical terminal to the functional module can be so prohibited, for example, following programming or testing of the functional module.
It will be noted that the technique of the invention can easily be duplicated within a single system (access to several modules and/or several accesses to one module). It can also easily be adapted to isolation between two functional modules.
The second dipole enables the preset voltage to be maintained for the terminal to the functional module after the fuse is broken. Thus, when the fuse has broken, the input to the functional module is permanently configured at a given value (which can in particular indicate to the module that it is henceforth isolated).
According to a first embodiment of the invention, the preset voltage is created internal to the system and/or corresponds to a predetermined logic level. For example, when the logic level is xe2x80x9c1,xe2x80x9d a pin is connected to a polarizing voltage of the functional module by way of an element having a resistance with a sufficiently high equivalent impedance value to not disrupt operation of the electrical terminal before the fuse breaks.
According to a second embodiment of the invention, when the logic level is xe2x80x9c0,xe2x80x9d the pin is connected to a polarizing voltage of the functional module by way of an element having a resistance with a sufficiently high equivalent impedance value so as to not disrupt operation of the electrical terminal before the fuse breaks.
Advantageously, the element with a resistance belongs to the group including, resistors, and MOSFET-type resistors. This list is by no means exhaustive. Indeed, it will be understood that any type of element having a high impedance value under the conditions of its operation and/or the operation of the system may be appropriate as an element with resistance.
Advantageously, the energizable semiconductor dipole belongs to the group including xe2x80x9czenerxe2x80x9d-type diodes and xe2x80x9ctransilxe2x80x9d-type diodes. However, it is clear that any type of dipole that provides a conducting state during operation by applying an isolating voltage to its terminals, may be appropriate.
According to one particular embodiment of the invention, the system has an internal device for generating the isolating voltage. It will be noted that the internal device for generating the isolating voltage can in particular be placed inside the functional module.
According to one embodiment of the invention, an external device for generating the isolating voltage, that the user can simply apply to the terminals of the system, can be provided.
In one particular embodiment of the invention, the functional module has a controller for controlling the internal device for generating the isolating voltage. According to this embodiment, the controller can be designed to control the external isolating voltage generator. Such a characteristic enables the system to function entirely autonomously since it no longer requires an additional external command.
The fuse may be made of any type of suitable material, for example, a nickel-chrome (or NiCr) alloy on a glass, alumina (or Al2O3) and/or ceramic substrate.
Advantageously, the electrical terminal is used for at least one of the operations belonging to the group, including programming of the functional module, configuration of the functional module, calibration of the functional module, receiving data or signals from the functional module, testing of the functional module, inserting a code into the functional module. It is clear that this list is, however, not exhaustive.
According to one advantageous embodiment of the invention, the system has at least two electrical terminals, each associated with different isolation device. It will be understood that the provision of a plurality of electrical terminals external to the functional module or system implies providing at least one fuse on each electrical terminal.
Preferably, the system belongs to the group including, integrated circuits (for example, hybrid or monolithic circuits), electronic circuits, and electrical circuits. Of course, this list is not exhaustive.
The invention also relates to an electrical isolating device of an electrical terminal of a functional module built into an electrical and/or electronic system, the functional module being connected to a supply voltage and connected external to the functional module by an electrical terminal via a pin. According to the invention, the isolating device electrically isolates the functional module, including a fuse whose first pole is connected to the pin of the functional module and the second pole corresponds to the external electrical terminal, a semiconductor dipole energizable under the influence of a priming voltage, a first pole of which is connected to the first pole of the fuse and the second pole is externally accessible to the device, a second dipole whose first pole is connected to the pin of the functional module and the second pole is connected to a preset voltage, such that application of a sufficient isolating voltage relative to the priming voltage between the second pole of the fuse and the second pole of the energizable semiconductor dipole causes physical breakage of the fuse, and thereafter, a preset voltage on the pin is exclusively maintained via the second dipole of the functional module. This voltage then enables the operation of the functional module to be controlled.
The invention also relates to an electrical isolating process designed to be used by the above-described system. According to the invention, the process includes a stage of electrically isolating the functional module by applying a sufficient isolating voltage relative to the priming voltage between the second pole of the fuse and the second pole of the energizable semiconductor dipole which causes physical breakage of the fuse, and thereafter, a preset voltage on the pin is exclusively maintained via the second dipole of the functional module. Thus, this voltage enables the operation of the functional module to be controlled.
The invention can in particular be used in an integrated electrical and/or electronic system used in powerful electromagnetic fields and/or ultraviolet radiation. Thus, the system is included in an environment belonging to the group that may include industrial environments, nuclear environments, and space environments.